


Protecting My Mate

by AbbyzHanson



Series: Undertale Requests [3]
Category: Undertale (Video Game)
Genre: Alternate Universe - Underfell (Undertale), Animal Instincts, Edge - Freeform, Edge isn’t too happy about it 😂, F/M, Implied Sexual Content, Mating Cycles/In Heat, Mild Sexual Content, Oops, Red - Freeform, Red let’s his heat take control for a min, Reverse Harem, Suggestive Themes, Underfell Papyrus (Undertale), Underfell Sans (Undertale), mentions
Language: English
Status: Completed
Published: 2020-07-16
Updated: 2020-07-16
Packaged: 2021-03-05 05:55:14
Rating: Mature
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 1,545
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/25309351
Author URL: https://archiveofourown.org/users/AbbyzHanson/pseuds/AbbyzHanson
Summary: After being questioned on why Red’s been acting off lately, it’s revealed that he’s going into heat soon.However, all the talk of primal instincts got you worked up and you can’t help but try  to make them kick in during an intimate moment.Edge may not approve since it could send the rest of them into heat early, but Red couldn’t care less.So what if they all come after you?They’ll have to go through him, he’s  protecting his mate anyways.
Relationships: Sans (Undertale)/Reader
Series: Undertale Requests [3]
Series URL: https://archiveofourown.org/series/1833367
Comments: 4
Kudos: 96





	Protecting My Mate

**Author's Note:**

> Written as a sort of follow up to this piece
> 
> https://imaginationstationgirl.tumblr.com/post/190900066173/mine
> 
> for a request from someone on my tumblr

Outside the house the sun was setting, it left beautiful colours behind in its wake. All it took was a look around the kitchen to see how much the lighting had changed its atmosphere. It was almost, sensual.

Suddenly, a soft yelp left your lips. Red had shortcutted behind you and licked your neck, a deep chuckle vibrating in his rib cage. When you scoffed and attempted to turn around he stalked closer, pressed your front against the counter and placed his skeletal hands on either side of you. However, instead of laughing and backing off like he’d usually do once he had his fun, he merely leant down and took a deep breath, taking in your scent.

Red had been behaving this way for the past couple of days and although it wasn’t unusual for him to act sexual, he had really taken it up a notch today. The more time went on, the more forward and aggressive he became. You knew that if you really didn’t want this he would stop, but so far, all you could seem to do was poorly chastise him for distracting you.

Giggling breathily you tried to turn and face him again, but the feeling of his nasal ridge nuzzling your ear and a quiet growl echoing in his chest made you stop.

“Red...?” You questioned, starting to feel a bit nervous, heat pooling in your stomach.

A hum of acknowledgement left his mouth and he pulled away slightly, as if he was coming out of some sort of trance.

“Are you ok?”

Sighing deeply, Red slipped his arms around your middle and answered.

“Yeh, m’ok. I’m startin’ my heat soon though.”

“Is that why you’re acting weird?”

Although you couldn’t see his face, you knew that comment must’ve hit a nerve because his claws began to grip you tighter and almost left a hole in your clothes. You couldn’t help but feel bad, you hadn’t meant it like that, this was important to him and you didn’t want him to think you didn’t care.

“Oh, sorry, that came out all wrong...”

Dark clouds drifted in the sky and you silently watched them float past while thinking of what to say next.

“I remember being told about the heats you guys go through. From the way it sounded though, I thought it was going to be a lot worse?”

Red chuckled sourly,

“Unfortunately Sweetheart, this is only the _beginning_ of my _pre_ -heat. I _wish_ this was the worst it could get.”

You could feel Red adjusting his hands so one was on your stomach while the other rested below your chest.

“As y’can probably tell, it’s gettin’ easier and easier to loose myself to instinct the closer I get to my full heat.”

Running one of his hands up and down your side, humming appreciatively, Red continued.

“‘Specially when a _delicious_ lil’ treat like yourself is walkin’ around... I can’t help but wanna take a bite.”

Your face flushed as you considering the ramifications of his words. Honestly you didn’t mind that he wanted to... he knows he could do it, especially with all the talk of primal instincts. You couldn’t deny how hot the concept was. Giggling lightly, a naughty plan began to form in your head, one that would give you both what you wanted and bring out the more animalistic side he spoke of.

Letting out a quiet whine, you arched your back and rubbed your ass against him. Red’s grip tightened considerably and he chuffed lightly at your movements. Your pulse raced as you started to feel the low vibrations coming from Red’s chest against your back, growl getting increasingly louder as you ground against his stiff magic.

Although you knew it wasn’t the smartest idea, the boys being unpredictable because of their heats and all, you keened softly and bared your neck for him. Red’s hands flew back to the counter top and gripped it so tightly between his claws that it left marks. Tilting his skull down again, a thick red tongue slowly rolled out of his mouth and licked at your pulse point, taking in a deep breath afterwards to smell you. You knew his control was wearing thin and you could feel his now barred teeth resting against the crook of your neck, your breath quickening by the minute... then, stillness.

Why wasn’t he doing anything? Why hadn’t he bit you yet? Trying to turn your head only got your stomach pinned against the counter by his pelvis but it had been enough to see the state of his eye lights.

Hazy, dilating and flicking back and forth like he was reacting to something.

These things made you wonder if he was hearing something that you couldn’t? Wasn’t that part of what set him off last time? Something startled him! Still desperately wanting him to bite you, you came to the conclusion that maybe spooking him yourself would work... There’s a spoon, maybe you could knock it off? Or a pan, you could hit the pa-

Suddenly, the door slammed open to reveal Edge and you nearly jumped out of your skin. But the yelp you let out was nothing compared to the sound you made as Red’s large maw suddenly opened wide, magic dripping onto your skin before it closed down on your shoulder, gripping it tightly as a ferocious growl slipped out from between his now occupied teeth.

Keening wantonly, you arched your back and braced yourself on the countertop so you wouldn’t fall. You couldn’t help it. In that moment it didn’t matter that you weren’t alone, Red was the only thing you felt. Suddenly, a light wave of magic pulsed through out the room and your legs went weak. You recognised it as Edge’s, it seems he wasn’t happy about finding the two of you in this compromising position.

“RED.”

Red chuffed against your neck, hot breath clashing with the wetness of your skin, obviously disapproving of his brothers tone of voice and use of his fake name.

Another, stronger pulse of magic flowed from Edge as he stepped closer.

“ **Sans**.”

Putting his knee between your thighs, Red turned his head slightly, his eyelights looking to Edge’s. However, they flickered back to you for a second when you tried to look too, a low whine leaving your lips. The feeling of Red’s tongue licking against your pulse point to calm you down sent tingles through body and heat to your core. You wondered if both the monsters in the room knew how you felt or if it was only Red? The glow of Edge’s cheekbones revealed that he knew too and he wasn’t as unaffected as he’d like to pretend...

“STOP THAT, WE BOTH KNOW WHAT WILL HAPPEN IF YOU CONTINUE! YOU’RE GOING TO MARK HER IN A WAY THAT WILL SEND INSTINCTS FLARING AND WE’LL ALL BEGIN OUR HEATS TOO EARLY.”

Sighing in pleasure as Red slowly ground into your ass, you responded to Edge, even though the question wasn’t really meant for you.

“Ya, but that was gunna happen anyways, _r-right_? Would it really be so bad if you guys started your heats a bit early?”

“YES, IT _WOULD_ , WE HAVE YET TO PREPARE FOR THEM! WE WOULD NOT ONLY BE PUTTING _OURSELVES_ AT RISK, But _You_ _Too_ And I Refuse To Let That Happen.”

Red’s teeth loosened their grip on your shoulder and fully turned his head to Edge, a single eyelight starting to glow brighter, leaving wisps of magic in the air.

“I’ll protect her.”

Shocked at hearing Red speak again you pouted, had he come out of the sexy animalistic zone he was in? God you hoped not, you weren’t gunna let Edge live it down if he had.

“Against Every Single One Of Us? I DON’T THINK SO...”

Red’s magic flared out and a thick growl echoed in the kitchen as he snapped his jaws at Edge. Your knees went weak again and you had to lean back into him, sighing deeply, an erotic need throbbing throughout your entire body. Red’s arms wrapped around you as Edge took a step forward, sockets going wide. You realised why Edge looked slightly panicked when, before you knew it, you were pulled into a shortcut by Red’s magic. Closing your eyes your hands clutched his ribs and you held on tight, praying you didn’t feel ill when it was over.

Like usual, when you opened your eyes in Red’s room you saw sheets sprawled across the floor and trash everywhere, but you didn’t feel grossed out, it was actually sorta comforting.

When you looked up you were met with hazy eyelights, bared teeth and a glowing bulge tenting Red’s shorts.

The feeling of his hard bones against your soft flesh left tingles on your skin and you couldn’t help but roll your hips up to meet his. Red ground back, growling lowly. However, you couldn’t stop thinking about the warning Edge gave and you stopped to question Red’s actions, just in case.

“Red, what are you doing?”

A pang of lust hit your gut the moment his teeth started curling into a devious grin, like a shark ready to snap up it’s prey, only three words breaking the silence.

“Protecting my mate.”

**Author's Note:**

> Thank you for reading, I hope you enjoyed it!
> 
> My writing blog is https://imaginationstationgirl.tumblr.com/
> 
> My main blog is https://abbyzhanson.tumblr.com/
> 
> My f/o and writing prompt blog is https://in-our-minds-in-our-hearts.tumblr.com/


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